1. Field of the Invention
This invention relates to an image analysis nonlinear adaptive filter and particularly to a nonlinear adaptive filter having an output whose frequency and attenuation characteristics are a function of the voltage value of the video signal noise characteristic.
2. Brief Description of the Prior Art
As is well known in the communication fields of audio and television transmission, there is often a need to improve the signal-to-noise ratio of the incoming signal. Similar needs extend to the field of image analysis where analog signals representing the image to be analyzed are processed to generate data descriptive of the objects in the image under analysis. In the past, the most common way to generally treat such signals is by the use of linear filters which reduce the overall bandwidth of the signal to make it as narrow as possible without severely degrading the desired signal information. This type of filter has been highly developed and culminates in the areas of filter design, in the optimal linear filter design, Wiener theory applications and other theoretical and practical techniques.
U.S. Pat. No. 3,694,776 entitled "Adaptive Filter Wherein Opposite Conductivity Transistors Are Operative In Response To Signals In Excess Of Predetermined Amplitude" for inventor D. Linder, issued Sept. 26, 1972, discloses a filter adaptive to attenuate as a function of the conduction of a transistor circuit wherein two coupled transistors of opposite polarity respectively conduct as a function of an error signal having an amplitude in excess of a predetermined value. This amplitude is generally unrelated to the peak-to-peak noise characteristic of the incoming signal and there is no provision to adjust this amplitude to match the noise of the incoming signal.